Ultra fast pulses the most efficient. Also for CO 2 capture with plasma

RODRIGUEZ OSUNA, ISAAC AARON; VALERIA CE ROMERO; FERNANDO MOLINA; DIANA GRONDONA; N OLAIZ

Conferencia; PLASMA CATALYSIS FOR CO2 RECYCLING; 2023

Here we report a novel system for the capture and conversion of CO2, an electro-reactor based on a high-fast pulsed electric field (HfPEF). We study the phenomenon of plasma-lysis in a nanochannel 200 nm high, 4 μm long, and 1 μm wide. Inside the nanochannel passes pure CO2 under normal conditions (1atm, 25°C). The flow rate in the nanochannel was 0.622 μl.h-1, and the residence time inside was 5.7 μs. The applied voltage was 20 V, the electric field of 1000 kV.m-1, and nano-pulses of 1, 100, and 500 ns of duration. The silico model was performed in COMSOL 5.5, 97 reactions [1][2][3] were studied to determine the best pulse profile to maximize the conversion effect of CO2 to other compounds such as carbon monoxide (CO), carbon (C), and oxygen (O). Also, three different conditions of the electric field, time on the pulse, and the delay between pulses were studied, to determine the best conditions that maximize energy efficiency. Figure 1 shows a summary of the results of the silico model. Figure 1.a shows the nanochannel geometry in the 2D domain with measurement. Figure 1.b shows the electric field distribution inside the nanochannel and an increase of the electric field around 1.25 times at the edges, due to the edge effect which is of interest for our model, because we consider the effects of the generation of electrons by field emission [4]. Figure 1.c shows the electron density distribution which is normal according to the standard plasma model [5]. Figure 1.D shows the heating of the electron and the linear increase of electron density during the pulse. We can observe a significant increase in the electron density with the time of the pulse but without reaching an electric discharge due to the short pulse times. It is important to highlight the increment in the average temperature of the electrons with the repetitions of the pulses, because this variable can increase the efficiency of the system, maximizing the conversion. Figure 1.E shows the generation of CO, C and O. When the pulse is activated we can observe a quick increment of these species (5.79%/ns for C).Another important variable is the ion concentration during and after the pulse, due to the ion-molecule interactions that favor the conversion of CO2 to CO, C, O, and O2. Figure 1.F shows the concentration of these ions and the post-pulse equilibrium time (around 9.23 ns). It is estimated that once this period has been reached, the additive effects of the species on the conversion of CO2 are negligible.